This study will use a prospective, naturalistic design to evaluate the hypothesis that sleep mediates the adverse effects of stress on health. Longitudinal assessment of psychobiological relationships among stress, sleep, and subsequent health outcomes in the proposed study represents the first attempt to prospectively evaluate how these important variables concurrently unfold across time to produce adaptation or disease. These data will be used to characterize psychobiological components of the stress-sleep relationship, as well as to refine models of adaptation and disease.